Quantification of contamination risk caused by radioisotopes released from the Fukushima Dai-ichi nuclear power plant is useful for excluding or reducing groundless rumors about food safety. Our new statistical approach made it possible to evaluate the risk for aquatic food and showed that the present contamination levels of radiocesiums are low overall. However, some freshwater species still have relatively high risks. We also suggest the necessity of refining data collection plans to reduce detection limits in the future, because a small number of precise measurements are more valuable than many measurements that are below detection limits.